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New Motor's in and having timing issue's ?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by twenty_below0, Aug 16, 2002.

  1. twenty_below0

    twenty_below0 1/2 ton status

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    New Motor\'s in and having timing issue\'s ?

    OK, got the new motor in and would like to know the CORRECT procedure for getting TRUE, tdc

    Put the dampener from the other engine and timing tab on this motor, dropped dist. in and started it. Was off the scale.
    The crank advance is 4 degrees and it has 6" rods so the dwell is longer, correct? I was told bring it up till it just stops ( # 1 on compression stroke) then mark balancer, go one full turn and mark again, now measure between the 2 marks and the middle is true top dead center? Is this correct? and if not would someone explain the true way to do this?

    Right now it's set by feel, advance it till it pings and then back off a little. It runs fair but still not right. Also what springs would you suggest? I put the medium ones in, they come on full at 2800 rpm's, the cam is a Crane with 216 intake and 228 exhaust at .050, But it has 1.6 rockers so lift is higher.Also the pistons call for a total of 34 degrees timing. Keith Black Hypereutectic pistons (Dont know if any of this matters) THX
     
  2. tipoil

    tipoil 1/2 ton status

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    Re: New Motor\'s in and having timing issue\'s ?

    For finding the tdc u have the correct method but did u use a tdc stop??? this tool#4795 if so ur ok,if not do it again!!

    For more info on this go to : comps cam page 22 and 23 step 5 to 7
     
  3. twenty_below0

    twenty_below0 1/2 ton status

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    Re: New Motor\'s in and having timing issue\'s ?

    THX for the link I will have to get this tool anyone else have suggestions?
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: New Motor\'s in and having timing issue\'s ?

    Shouldn't really matter. Advancing the cam only changes the valve timing relative to the crankshaft position. The timing mark only cares where the piston is at in its travel. Same goes for the piston, it'll reach the top of its travel faster and stay there longer with that 6 inch. TDC is still right smack between when the piston reaches its highest point and until it starts to move down. You'll have a little more cylinder pressure with those big rods. Set your intial timing for 14 degrees and run about 8-12 degrees vac advance on timed vacuum if you have an HEI and a Q-Jet. If you don't have a Q-Jet than hopefully you'll have a decent timed port. You just want a port in the throttle body thats covered by the throttle blade at idle and becomes uncovered when the throttle opens. Some other carbs have a port right in the venturi whichs sucks more vacuum the wider you have the throttle, which defeats the point of vacuum advance. Nothing wrong with full manifold vacuum, but I find ported a little easier to work with.
     
  5. twenty_below0

    twenty_below0 1/2 ton status

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    Re: New Motor\'s in and having timing issue\'s ?

    I do have a Q-jet, could you go over the exact procedure for getting the true TDC one more time....I want to make sure I am doing this right.My tab sits at about 2:30 on the balancer.Sorry dont mean to be annoying
     
  6. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: New Motor\'s in and having timing issue\'s ?

    If you have the same crank, timing cover, and balancer, things should be fine. You got the right idea when you described finding TDC. You can buy a stop from comp cams that screws in like a spark plug. The stop doesn't have to stop the piston exactly at the top of its travel, just near it. So with the stop in, rotate the engine over by hand clockwise. You want the piston in #1 to contact the stop and halt your motion. Don't crank it hard, just enough so the piston just makes contact. Once you stoped, make a mark on the balancer where your timing tab says 0. Then, swing the motor one turn counter clockwise until you stop again. Make another mark on the balancer where your tab says 0. Halfway between thses marks will be TDC. TDC is not simply when the piston reaches the top of its travel. It'll reach its maximum height and stay there for a bit before comming down. Thats why you have to make two marks, right smack in the middle of the time the pistons hangs around at its maximum height is TDC.
     

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